1. Field of the Invention
This invention relates to heat-actuated heat pumping apparatus and process having two working chambers to provide a Vuilleumier cycle for space conditioning, including space cooling and heating, refrigeration, hot water heating, and cryogenic applications. Gaseous working fluid is displaced through sets of heat exchangers in a phased relationship by means of externally or internally driven displacers between two working chamber volumes. The working chamber volumes are in pressure communication with each other in the vicinity of intermediate thermal exchange means in each volume equalizing the pressure between the two working volumes with one module acting as the driver for the heat pumping action (refrigeration) of the second module. The pressure communication between the two working volumes may be through a floating piston thereby providing two different intermediate heat levels, resulting in a four temperature level Vuilleumier heat pump. The apparatus and process of this invention reduces mechanical complexity and improves thermal exchange in a heat pump apparatus suitable for large air conditioning applications as well as small refrigeration and cryogenic applications.
2. Description of the Prior Art
Stirling cycle engines are well known for compressing or expanding a gas working fluid for power or refrigeration uses. Stirling cycle engines are generally classified as opposed piston engines or displacer piston engines which, in order to obtain double-acting Stirling engines, have required multiple pistons and have been bulky with large dead volumes. U.S. Pat. No. 3,460,344 teaches a double-acting Stirling engine employing a single cylinder by use of vanes to coordinate the working fluid motion thereby eliminating reciprocating motion between the crankcase and working chambers and reducing the problem of sealing the working fluid from the crankcase.
U.S. Pat. No. 4,253,859 relates to a Kirk cycle gas refrigerator utilizing rod members to effect volumetric changes of a refrigerating medium to produce low temperatures. A floating piston is used between a driving cylinder and an expansion cylinder.
U.S. Pat. No. 3,474,641 teaches a heat-actuated regenerative compressor for operation between fixed pressures providing movement of gas by an oscillatory displacer through a cooler, regenerator and heater which may be used as a prime mover or through a pressure sensitive means may be used to pump a refrigerant through a condensation-expansion-evaporation-compression cooling cycle. U.S. Pat. No. 3,521,461 teaches operation of a heat-actuated regenerative compressor of the U.S. Pat. No. 3,474,641 in conjunction with a pneumatic assisted linkage with a refrigerant in a compression-condensation-expansion-evaporation cooling cycle that permits operation of the power and refrigeration cycles at different average pressures, allowing the power cycle to be at higher pressure than the refrigeration cycle, thereby increasing specific output. U.S. Pat. No. 3,716,988 teaches a heat-actuated regenerative compressor in combination with an expansion device which extracts work, such as a piston or rotary expander which is isolated from the active volume of the compressor and is at different pressures and temperatures than the compressor at the time of extraction of energy. The apparatus is advantageously used as a prime mover and in conjunction with pumping systems. U.S. Pat. No. 3,690,113 teaches a cyclic gas cooling apparatus and process wherein a thermal compressor and thermal regenerative means is in communication with a pressure regenerative means for use in air conditioning systems.
Vuilleumier cycles and variations thereof are known; U.S. Pat. No. 1,275,507 teaching an elementary Vuilleumier cycle and apparatus; U.S. Pat. No. 3,151,466 teaching Vuilleumier cryogenic cycles, all ideally maintaining time-varying, spacially-uniform pressure throughout the fluid system. The apparatus of both the U.S. Pat. Nos. 1,275,507 and 3,151,466 operates with reciprocating cylindrical displacers. U.S. Pat. No. 3,630,041 teaches an improvement of the Vuilleumier cycle refrigerator providing that the hot and cold cylinders are physically separated with an independent drive means for each displacer. Another modification of the Vuilleumier refrigerator is taught by U.S. Pat. No. 3,862,546 providing very rapid and high thermal heat-up by using electric resistance heating elements which change their resistance in the desired temperature range. Another modification of the Vuilleumier refrigerator cycle is taught by U.S. Pat. No. 4,024,727 which has a separate pneumatically operated cold displacer to produce cryogenic refrigeration.